1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel capable of improving color purity and contrast by preventing light emitted from fluorescent layers from being reflected by a side of each bus electrode again when ultraviolet rays excite the fluorescent layer of the inside of each cell and the light is emitted from the fluorescent layer.
2. Background of the Related Art
FIG. 1 is an exploded perspective view showing a state that a conventional plasma display panel is separated, and FIG. 2 is a sectional view showing an arrangement state of electrodes.
A rear panel 20 shown in FIG. 2 is rotated at an angle of 90 degrees to a front panel 10.
A plasma display panel is that the front panel 10, which is a display surface for displaying image, and the rear panel 20, which forms a rear surface of the plasma display panel, are coupled parallel at a certain distance from each other.
On a side of the front panel 10, arranged are sustain electrodes for maintaining the light emission of the cells by mutual electric discharge in one pixel, that is, common sustain electrodes X and scan sustain electrodes Y, which are forms a pair respectively. The sustain electrodes include transparent electrodes (or ITO electrodes) Xa and Ya made of transparent Indium Tin Oxide material and bus electrodes Xb and Yb made of metal material, and a black layer B, which is made of ruthenium oxide (RU2O) and red lead (PbO) or carbon group, is formed between the transparent electrodes and the bus electrodes.
Furthermore, the common sustain electrodes X and the scan sustain electrodes Y are covered with a dielectric layer 12 for restricting discharge current and insulating between the pairs of electrodes, and a protection layer 13 is formed on an upper surface of the dielectric layer 12.
Moreover, the scan sustain electrode Y carries out a function of a scan electrode for forming wall charge by causing electric discharge during an initial operation of the plasma display panel and the common sustain electrode X carries out a function of a common electrode for applying AC voltage during the electric discharge.
The rear panel 20 includes barrier 21 of a stripe type (or a dot type) arranged parallel for forming a plurality of discharge spaces, i.e., the cells C, a plurality of address electrodes A arranged parallel to the barrier 21 at portions intersecting with the sustain electrodes 11 for performing address discharge to generate vacuum ultraviolet rays, and a dielectric layer 22 formed on upper portions of the address electrodes.
Additionally, on an upper surface of the rear panel, i.e., the surface besides the upper end surfaces of the barrier 21, covered are red, green and blue (R, G and B) fluorescent layers 23 to emit visible rays for displaying image.
An image display process of the cells of a conventional PDP having the above structure will be described in brief.
Initially, if voltage of 150Vxcx9c300V is supplied between the scan sustain electrode Y and the address electrode A inside an arbitrary discharge cell, writing discharge is generated in the inside of the cell located between the scan sustain electrode Y and the address electrode A, and thereby wall charge is formed on the dielectric layer adjoining the inside of the corresponding discharge space.
After that, if discharge voltage above 150V is supplied to the corresponding common sustain electrode X and scan sustain electrode Y, sustain discharge is generated between the common sustain electrode X and the scan sustain electrode Y in the corresponding cell.
That is, the electric discharge between the electrodes generates electric field inside the cell, and thereby a small amount of electrons in discharge gas are accelerated. The accelerated electrons and neutral particles in gas come into collision, thereby being ionized into electrons and ions. The ionized electrons come into collision with neutral particles, and the neutral particles are rapidly ionized into electrons and ions, so that the discharge gas is made into a plasma condition, and at the same time, vacuum ultraviolet rays are generated.
The generated ultraviolet rays excite the fluorescent layers 23 to generate visible rays. If the generated visible rays are emitted to the outside through the front panel 10, the emission of the arbitrary cell, i.e., the image display may be recognized from the outside.
However, in the front panel of the plasma display panel, especially, the bus electrodes Xb and Yb formed on the front panel 10 causes the following problem.
A side of each bus electrode Xb and Yb adjoining the dielectric layer 12 faces the inside of the cell C and has a peculiar color of silver (Ag).
Therefore, when the ultraviolet rays excite the fluorescent layer 23 inside the cell C and generate the visible rays, the side of each bus electrode Xb and Yb reflects the light reflected from the fluorescent layer 23 again, and thereby the light reflected again is displayed on the display surface of the front panel 10, which is the outside of the cell C.
As a result, silver (Ag) forming the bus electrodes Xb and Yb has its own peculiar color, and the color of the light reflected is not even due to the property of the bus electrodes when the bus electrodes Xa and Ya reflects again the light emitted from the fluorescent layers of R, G and B colors. Especially, because the B (Blue) light is relatively reflected less, when a user sees a screen in an off condition of the cell C, the screen shows somewhat yellow color as a whole.
Therefore, the conventional plasma display panel has several problems that the color purity generated on the fluorescent layer itself is deteriorated and that the contrast is deteriorated if the product is installed on a place where there is external light.
The above problems are severer when plural pairs of sustain electrodes in a single cell exist.
Accordingly, the present invention is directed to a plasma display panel that substantially obviates one or more problems due to limitations and disadvantages of the prior art.
An object of the present invention is to provide a plasma display panel capable of improving color purity by preventing light emitted from fluorescent layers from being reflected by a side of each bus electrode again when ultraviolet rays excite the fluorescent layer of the inside of each cell and the light is emitted from the fluorescent layer.
Another object of the present invention is to provide a plasma display panel capable of improving contrast by absorbing light emitted inside the cell through the bus electrode directing the inside of the cell.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a plasma display panel includes: a pair of panels facing at a prescribed interval from each other; sustain electrodes having a plurality of transparent electrodes arranged on one of the panels and bus electrodes formed to be at least partially overlapped on the transparent electrodes, the sustain electrodes being in pairs; address electrodes arranged to intersect the pairs of sustain electrodes; a plurality of cells formed on intersecting points of the pairs of sustain electrodes and the address electrodes; barrier formed between the panels for dividing the cells; and fluorescent layers arranged between the barrier, wherein a light absorption layer for absorbing light of each fluorescent layer formed on the cell is provided on a side of each bus electrode directing the inside of the cell.
Preferably, the light absorption layer is formed by mixing and firing ruthenium oxide (RU2O) and lead oxide (PbO)
Preferably, the light absorption layer is formed by firing carbon.
Preferably, the light absorption layer has conductivity.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.